mlxsw: core_acl_flex_actions: Return error for conflicting actions

Spectrum switch ACL action set is built in groups of three actions
which may point to additional actions. A group holds a single record
which can be set as goto record for pointing at a following group
or can be set to mark the termination of the lookup. This is perfectly
adequate for handling a series of actions to be executed on a packet.
While the SW model allows configuration of conflicting actions
where it is clear that some actions will never execute, the mlxsw
driver must block such configurations as it creates a conflict
over the single terminate/goto record value.

For a conflicting actions configuration such as:

 # tc filter add dev swp49 parent ffff: \
   protocol ip pref 10 \
   flower skip_sw dst_ip 192.168.101.1 \
   action goto chain 100 \
   action mirred egress mirror dev swp4

Where it is clear that the last action will never execute, the
mlxsw driver was issuing a warning instead of returning an error.
Therefore replace that warning with an error for this specific
case.

Fixes: 4cda7d8d ("mlxsw: core: Introduce flexible actions support")
Signed-off-by: Nir Dotan <nird@mellanox.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>